1. Field of the Invention
The present invention relates to a robot for handling flat panels such as liquid crystal displays during processing of such panels in a vacuum. In particular the robot system of this invention operates in a vacuum using linear motion.
2. Brief Description of Related Developments
Many different types of robots exist for use in the processing of semiconductor and other components in an evacuated environment. These robots generally have multiple axes of movement which must occur within a confined area, i.e., within a vacuum chamber. It is desirable therefore, to construct the moving elements of the robot in a manner which limits the operational area (foot print) of the robot. This is generally accomplished by providing rotating and translating linkages which move the work piece holder (end effector) through a path in which the work piece is picked up, processed and returned for transport.
The processing of semiconductors often involves multiple process steps, such as, the deposit of a film on a substrate by chemical vapor deposition (CVD), the photo etching of the film, heating, cooling and cleaning.
The process operations are generally performed under vacuum in a specialized process chamber. Because of the need for improved efficiency of each process, batch processing of semiconductor substrates has generally been used for substrate processing. This is because, for each process step, the process chamber must be vented, the substrate loaded, the chamber sealed and pumped to vacuum. After processing, the steps are reversed.
To improve the process efficiency, a cluster of processing chambers are arranged around a substrate transport chamber which is constructed to be kept under vacuum. One or more load lock chambers are connected through slit valves to the transport chamber.
The load locks accommodate cassettes of substrates to be processed. The cassettes are delivered to the load lock by the front end delivery transport of the system. A load lock constructed to accommodate such cassettes is shown in U.S. Pat. No. 5,664,925 owned in common with the subject application. The disclosure of the ""925 patent is incorporated herein by reference, in its entirety.
In this manner cycling times are reduced, while significantly increasing system throughput. The process and transport chambers are maintained continuously under vacuum, while only the load lock is cycled. The load lock receives the substrates to be processed after being sealed from the transport chamber and vented to atmosphere. The front end port is than sealed and the load lock is pumped to a vacuum consistent with the transport and processing chambers.
A robotic transfer mechanism is mounted within the transport chamber and operates to remove substrates from the load lock and deliver them to the selected process chambers. After processing, the substrates are picked up by the robot and transported to the next process chamber or to a load lock for removal from the transport chamber. In some instances, for timing purposes, these systems may employ buffer stations which are adapted to store substrates either before loading or at other times during the transport of the substrate through the system. The
A system of this type is described in U.S. Pat. No. 5,882,413 and an example of a robotic transfer mechanism is shown in U.S. Pat. No. 5,647,724, each of which is assigned to a owner common to this application. The disclosures of these patents are incorporated herein by reference in their entirety.
As such systems are used for larger and larger semiconductor devices, such as liquid crystal displays and the like, the challenge of generating the required movement of the substrate through its processing path within as compact a space as possible becomes significant. As shown in the linkage systems of the above referenced patents, a series of rotating linkages, such as a SCARA, or two link robot arm linkage, are actuated through rotary drives to translate the end effector of the robot through the desired trajectory. In some instances it would be desirable to use linear movement to obtain the desired directory because of its small foot print. This may be even more desirable where large substrates are being processed. An example of a system using linear movement is shown in U.S. Pat. No. 4,715,921. In particular the embodiments of FIGS. 4 and 11(a) of the ""921 patent illustrated linear movement style mechanisms. Linear mechanisms, however, are generally known to be dirty, in that considerable particle contamination may be generated by the linear bearings and cable and pulley drive mechanisms.
It is the purpose of this invention to construct a robot for use in processing generally larger substrates in a vacuum, where the end effector uses linear motion in its trajectory. It is a further object of this invention to provide a robot having an end effector that is mounted on linear bearings and is cable driven. It is a further object of this invention to construct a robot system having a cable driven end effector which is mounted on linear bearings in which system contamination from the linear bearings and cable drive is minimized.
The present invention is directed to a robot system for transporting substrates for processing within a vacuum chamber. It is illustrated in conjunction with a batch processing system with multiple processing stations interconnected by a central transport chamber. Substrates are delivered or picked up from an external loading station through one or more load locks which cycle from vacuum to atmosphere by operation of appropriate slide valves. The transport mechanism of this invention may also be designed to service a single processing chamber.
The system of this invention utilizes a robot body which extends into the transport chamber and houses a rotary drive mechanism and components, such as wires and conduits which are isolated from the vacuum. An axially extended shaft is driven by the drive mechanism and extends upward from the robot body. The shaft is driven both axially and in rotation to provide vertical and rotary positioning. The housing within the robot body is generally maintained at atmospheric pressure. In addition the robot body forms a pedestal to support a linear motion assembly for rotation on the shaft about a vertical axis of the robot body.
The linear motion assembly comprises a U-shaped component housing which forms a sealed enclosure for the linear motion drive system. The U-shaped component housing is mounted on the shaft of the robot body for rotary motion therewith. The linear motion assembly further includes upper and lower end effectors supported on elongated wrist sections. The wrist sections are mounted for linear motion on linear bearings which are oriented transverse to the axis of the robot body. Since the end effectors are mounted on the U-shaped housing, they can be conveniently stacked one over the other, which provides a significant reduction in the footprint of a dual effector system.
The U-shaped component houses the drive motors, control components, wires and conduits for the linear drive of the linear motion assembly. Two leg sections support the linear bearings in their transverse orientation, one above the other. The linear drive motors, housed in each leg section, are mechanically connected through a dynamic seal to a pulley and cable system which is connected to drive the end effectors on the linear bearings. To minimize contamination, a labyrinth seal is constructed at the bottom of the linear bearings. These seals operate to prevent particles from the cable and pulley drive system and the linear bearings from entering the vacuum chamber and contaminating the substrate.
Through appropriate control algorithms executable by microprocessors located in the bridge portion of the U-shaped housing, the end effectors can be reciprocally activated to load and unload substrates to or from a process chamber.
In this manner, a robot system is constructed which provides rotary motion of the linear motion assembly about the axis of the robot body, vertical motion of the linear motion assembly on the axis of the robot body, and linear motion of the end effectors on the linear bearings.